The present invention relates to a thermal anti-icing system for an aircraft engine. Examples of the invention relate to a thermal anti-icing system for an air intake duct. The air intake duct may be for an engine, a cooler of an engine, an aircraft engine for example a gas turbine engine, or a gas turbine engine for other than an aircraft amongst other examples.
U.S. Pat. No. 5,011,098 discloses a thermal anti-icing system for an unducted fan (UDF) engine. The blades of the fan are mounted at the rear of a gas turbine engine outside the engine. If ice forms on the housing or cowling of the engine and separates from the cowling it may damage the fan blades. In order to reduce icing a thermal anti icing system is provided which uses hot air bled from the engine to heat cowling locations subject to significant icing. The cowling has a surface referred to as a skin. The leading edge of the cowling has a space defined by a bulkhead within the cowling and the outer skin of the cowling. Hot air bled from the engine is supplied to a tube of piccolo type inside the space. Part of the skin within the space is provided by a double skin heat exchanger with a plurality of flow passages. The flow passages are spaced apart and extend in the direction of the axis of the gas turbine engine. The spaces between the flow passages are heated by conduction through the material of the skin. The heat exchanger is provided at a location where, if ice is formed and shed from the cowling, there would be a risk of damage to the fan blades; that is over the outer surface of the cowling having an air flow leading to the unducted fan blades. Other parts of the space have a single skin. Hot air from the piccolo tube is caused to flow through the heat exchanger, heating the skin of the cowling more than the single skin parts of the cowling.
U.S. Pat. No. 3,933,327 describes an anti-icing plenum wherein the leading edge of a jet engine nacelle is provided with a structure to prevent the formation of ice particle at the inlet of the jet engine. A leading chamber of the nacelle is formed with a double skin generally facing to the interior towards the jet engine. Hot exhaust gases from the jet engine are passed into spaced channels formed between the inner and outer skins to heat the outer skin from the inside thereof.